linux/net/dns_resolver/dns_key.c

/* Key type used to cache DNS lookups made by the kernel
 *
 * See Documentation/networking/dns_resolver.rst
 *
 *   Copyright (c) 2007 Igor Mammedov
 *   Author(s): Igor Mammedov ([email protected])
 *              Steve French ([email protected])
 *              Wang Lei ([email protected])
 *		David Howells ([email protected])
 *
 *   This library is free software; you can redistribute it and/or modify
 *   it under the terms of the GNU Lesser General Public License as published
 *   by the Free Software Foundation; either version 2.1 of the License, or
 *   (at your option) any later version.
 *
 *   This library is distributed in the hope that it will be useful,
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See
 *   the GNU Lesser General Public License for more details.
 *
 *   You should have received a copy of the GNU Lesser General Public License
 *   along with this library; if not, see <http://www.gnu.org/licenses/>.
 */
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/slab.h>
#include <linux/string.h>
#include <linux/kernel.h>
#include <linux/keyctl.h>
#include <linux/err.h>
#include <linux/seq_file.h>
#include <linux/dns_resolver.h>
#include <keys/dns_resolver-type.h>
#include <keys/user-type.h>
#include "internal.h"

MODULE_DESCRIPTION(…) …;
MODULE_AUTHOR(…) …;
MODULE_LICENSE(…) …;

unsigned int dns_resolver_debug;
module_param_named(debug, dns_resolver_debug, uint, 0644);
MODULE_PARM_DESC(…) …;

const struct cred *dns_resolver_cache;

#define DNS_ERRORNO_OPTION …

/*
 * Preparse instantiation data for a dns_resolver key.
 *
 * For normal hostname lookups, the data must be a NUL-terminated string, with
 * the NUL char accounted in datalen.
 *
 * If the data contains a '#' characters, then we take the clause after each
 * one to be an option of the form 'key=value'.  The actual data of interest is
 * the string leading up to the first '#'.  For instance:
 *
 *        "ip1,ip2,...#foo=bar"
 *
 * For server list requests, the data must begin with a NUL char and be
 * followed by a byte indicating the version of the data format.  Version 1
 * looks something like (note this is packed):
 *
 *	u8      Non-string marker (ie. 0)
 *	u8	Content (DNS_PAYLOAD_IS_*)
 *	u8	Version (e.g. 1)
 *	u8	Source of server list
 *	u8	Lookup status of server list
 *	u8	Number of servers
 *	foreach-server {
 *		__le16	Name length
 *		__le16	Priority (as per SRV record, low first)
 *		__le16	Weight (as per SRV record, higher first)
 *		__le16	Port
 *		u8	Source of address list
 *		u8	Lookup status of address list
 *		u8	Protocol (DNS_SERVER_PROTOCOL_*)
 *		u8	Number of addresses
 *		char[]	Name (not NUL-terminated)
 *		foreach-address {
 *			u8		Family (DNS_ADDRESS_IS_*)
 *			union {
 *				u8[4]	ipv4_addr
 *				u8[16]	ipv6_addr
 *			}
 *		}
 *	}
 *
 */
static int
dns_resolver_preparse(struct key_preparsed_payload *prep)
{ … }

/*
 * Clean up the preparse data
 */
static void dns_resolver_free_preparse(struct key_preparsed_payload *prep)
{ … }

/*
 * The description is of the form "[<type>:]<domain_name>"
 *
 * The domain name may be a simple name or an absolute domain name (which
 * should end with a period).  The domain name is case-independent.
 */
static bool dns_resolver_cmp(const struct key *key,
			     const struct key_match_data *match_data)
{ … }

/*
 * Preparse the match criterion.
 */
static int dns_resolver_match_preparse(struct key_match_data *match_data)
{ … }

/*
 * Describe a DNS key
 */
static void dns_resolver_describe(const struct key *key, struct seq_file *m)
{ … }

/*
 * read the DNS data
 * - the key's semaphore is read-locked
 */
static long dns_resolver_read(const struct key *key,
			      char *buffer, size_t buflen)
{ … }

struct key_type key_type_dns_resolver = …;

static int __init init_dns_resolver(void)
{ … }

static void __exit exit_dns_resolver(void)
{ … }

module_init(…) …
module_exit(…)
MODULE_LICENSE(…) …;